Controlled combustion is a prerequisite for efficient, low-emission engine operation. Knocking occurs when the air-fuel mixture self-ignites prematurely. Sustained knocking combustion causes damage primarily to the cylinder head gasket and cylinder head. Engine management can reduce the risk of knocking by adopting a later ignition point. The aim, however, is to obtain the maximum energy yield from varying qualities of fuel by utilizing an ignition point that is as early as possible.